STATE DEPARTMENT - International efforts to limit Iran's nuclear program have entered a new phase with the outline of what a final agreement might look like. But talks could drag on beyond July's deadline, adding to pressure on both Washington and Tehran.

Getting Iran to talks to limit its nuclear program is one of the biggest foreign policy accomplishments of the Obama administration, an opportunity that the president says shows the strength of international resolve.

"The odds of success are still long, and we reserve all options to prevent Iran from obtaining a nuclear weapon," said President Barack Obama. "But for the first time in a decade, we have a very real chance of achieving a breakthrough agreement - one that is more effective and durable than what would be achieved through the use of force."

Talks in Vienna have made progress, but there is not yet agreement on lifting some sanctions in exchange for Iran rolling back parts of its nuclear program.

Iranian President Hassan Rouhani says there is no rush.

"If some countries behind the scenes who want to create problems are not given a chance to sabotage talks, then we have enough time to achieve the ultimate success," he said. "[If] we don't come to an agreement by that deadline, we can extend that interim agreement for another six months. But I think it will be done by the proper time."

Extending talks could be a problem for Obama as some of his political opponents want new sanctions against Iran.

"I think if we hear from those talks that they need another six months that's pretty bad news because it will be very difficult for President Obama to deal with the Congress during mid-term elections when the Republicans are now favored to even take the Senate," said American University professor Hillary Mann Leverett.

The president could keep working around Congress with six-month waivers on some sanctions, but Leverett says Iran is holding out for more.

"The Iranian aim is to get investment into oil and gas," Leverett continued. "These are 10-year projects at the very minimum. You can't really do it six months, six months, six months. So I think the Obama administration is now realizing that, to get the deal that it wants, it really may need to go to Congress to lift the sanctions."

The Iran nuclear deal may be less of a political issue if talks are extended while Congress is out of session. Former U.S. ambassador Adam Ereli says the timetable favors the president.

"The politics constraining Obama are much less onerous or much less of an obstacle than the politics constraining the Iranian negotiators," he said.

At a time when many Iranians want Rouhani to get sanctions lifted to improve the economy, Ereli says Tehran's nuclear negotiators are under pressure from hardliners who want to maintain the threat.

"If they don't come up with a deal, or if what they are proposing is too much for their political rivals in Iran, then they could find themselves facing a backlash as well," he said. "So again, I think it works both ways on this."

Throughout these talks, the Obama administration must also continue to reassure Israel that Washington will not allow Tehran to develop a nuclear weapon.